Eastern Sierra, Inyo County, California, USA May 5, 2022
~4150' elevation, Bishop.
A few of these bees were nectaring on Palmer's Penstemon (Penstemon palmeri) in a residential native garden.
I'm guessing this might be a female? It was quite a bit bigger & was being followed by a smaller solid black bee as it nectared.
If another small black bee came within the bigger bee as it nectared, a fight ensued between the 2 smaller black bees.